@devil240z: Wasn't it just the little board of a keyboard? Not sure why you'd need something special. Just get the connections of the button to run into the keyboard controller, making it act like a single key input.

A Teensy is essentially a very small Arduino. They cost around $13 and is about the size of a stick of gum. Pretty much any code you find for Arduino projects can be loaded on a Teensy.

Some of the cooler things it can do that the Arduino doesn't do natively is that it can emulate a keyboard, mouse, or Joystick. This is most likely what their code is doing. When an input pin is pulled low, it types something into a web form they made.